Results are described of an experiment made at the Indian Agricultural Research Institute, New Delhi, for 4 years under semi-arid seasonally dry tropical conditions to explore the possibilities of double cropping in the traditionally monocropped areas. Use of straw mulch did not increase mung yield in the monsoon season with welldistributed rainfall but increased its yield in a year when the monsoon receded early. Irrespective of rainfall pattern, mulching helped conserve enough moisture in the top 30 cm of soil to enable germination and quick establishment of the rapeseed crop. Mulching continued in the rapeseed crop conserved soil moisture until the flowering stage and increased the yield of rapeseed by 23%. Kaolin, a reflectant material applied at the preflowering stage, also increased seed yield of rapeseed.

Mature plant characters and yield components were measured on a two-row (Proctor) and a six-row (Clermont) spring barley variety, the F1 of the cross between them, and the first back-cross to each parent.

Whereas shoot dry weight in the F1 significantly exceeded the mid-parental value, and chaff dry weight, stem length and weight per grain showed positive heterosis, grain yield did not exceed the mid-parental value and number of grains per plant showed negative heterosis.

A scaling test showed that an additive-dominance model fitted the data in all cases except possibly for dry weight per grain, where the χ2 test approached significance.

The partial dominance of the two-row allele (V) for grains set per rachis node exhibited in the mature ears of the F1 was not apparent at anthesis when all the lateral florets were found to have large, apparently normal stamens. However, the ratio of median to lateral grains set over all main shoot ears of the F1 was 1:0·21 with an average of six lateral grains per ear.

The results presented indicate that the factors determining total dry-matter production and grain yield are inherited in such a way that the restriction upon grain yield in the F1 is due not to a deficiency of dry matter but to a limited capacity of the plant to store dry matter in the form of grain. This may indicate some developmental interdependence in the expression of yield component characters.

Leaf and tiller production, ear development and ear growth were measured on a two-row and a six-row spring barley genotype, on the F1 between them and on the first backcrosses.

Among the developmental differences between the parental genotypes the following appeared to be of particular significance: the two-row genotype bore more leaves on the main shoot than the six-row genotype and these were initiated more slowly, but emerged more rapidly; the two-row genotype had a proportionately longer ear initiation phase than the six-row; the apical dome was bigger in the six-row than in t he tworow; the two-row genotype produced more tillers.

The association of characteristics with ear type may depend on a pleiotropic effect of the ear type (V – v) locus or, alternatively, some of these characteristics may be under independent genetic control. The latter hypothesis was supported by the developmental pattern of the F1.

It may be that well-adapted two-row and six-row genotypes have patterns of development balanced for the particular ear type. Hybridization between ear types may disrupt these balanced developmental patterns producing a high frequency of poorly adapted genotypes in the progeny.

A seedling test for measuring cold hardiness in Lolium perenne cultivars is described. Seedling performances of the cultivars in this test were closely related to those of mature plants in an artificial freezing test and to reported survival under field conditions in U.K. winters.

With two-leaf seedlings it was possible to analyse hardiness into leaf damage, regrowth and plant kill enabling an index of hardiness to be compounded. Using this index in conjunction with lethal dose 50% estimates, meaningful separation of cultivars was possible.

The possible application of this technique for screening breeding material and for detailed physiological work is discussed.

Seeds from individual heads of wild safflower (Carihamus oxyacantha Bieb.) plants collected from five locations were used in this study. Locations were situated on a roughly east-west transect passing through Shiraz, Iran. The western locations were cooler with higher annual rainfall than the eastern sites. Wild safflower plants of different locations produced about an average of 150 heads per plant, but only 60% of them contained seeds. Frequency distributions constructed for number of seeds per head, germination percentage, and seedling length showed trends of change in the skewness of the distribution for the latter two characteristics parallel to the environmental selective pressure, i.e. the skewness was towards the left for eastern locations but it gradually moved to the right for western ones. Striking amounts of polymorphism were also observed for these characters. A very high proportion of total variance was concerned with differences between heads of the same plant for number of seeds, germination ercentage, and seedling length. Very little variability was found among plants of the same ecotype.

Crop yield results from three long-term drainage experiments are analysed and show that increases of up to 1 t/ha of winter wheat can be attributed to the effect of drainage. Mole drainage is clearly the preferred treatment on heavy clay soils. There is also a suggestion that drainage permits more efficient utilization of nitrogen.

The correlation between sorption and mobility of potassium in illitic soils has been used to compare K leaching in profiles under different fertilizer treatments in longterm experiments. Estimates of potassium saturation of the cation exchange capacity in 15 cm soil layers to a depth of 225 cm indicated maximum leaching of K in unfertilized soils. Application of N, P and K increased K uptake by plants, reduced K saturation and thus its leaching.

Tubers produced by potato plants grown in vermiculite and supplied with either 0, 1 or 3 mM calcium chloride solution developed brown necrotic lesions of internal rust spot. Plants supplied with 9 and 27 mM calcium chloride solution did not show the symptoms and had a substantially greater concentration of calcium in the tuber dry matter. It is concluded that internal rust spot is a physiological disorder associated with a low concentration of calcium in the affected tubers.

In many field investigations of cereal growth, stages of crop development may be described adequately using the Feekes scale (Large, 1954) or the more recent decimal code (Zadoks, Chang & Konzak, 1974). For example, the onset of stem extension (Feekes stage 6; decimal code 31) is frequently taken as a field indication of the switch from vegetative to reproductive growth. However, in investigations of the influence of soil properties, especially temperature, on shoot apex and leaf growth, it is important to know (a) the position of the apex below the soil surface during the early stages of development and (b) the timing of the rise of the apex above the soil surface.

A wealth of information is available concerning the ‘normal’ gastrointestinal mechanisms within various species of herbivores (Alexander, 1962; Church, 1971; Quarterman, Phillips & Lampkin, 1957). In addition, the effect that dehydration has upon the physiology of digestion has also been investigated (Schmidt-Nielsen et al. 1956; Schmidt-Nielsen, 1964; Maloiy, 1972; Macfarlane et al. 1972). This communication presents preliminary observations on the effect that dehydration hasupon gastrointestinal water content, as a percentage of total gut contents, and fluid osmolality (m-osmol/kg H2O). A comparison was made under controlled laboratory conditions between six species of domestic herbivores fed identical diets and exposed to a simulated desert environment

An observed positive correlation between tuber sprout growth in store and yield and tuber weight was due to the association of short sprouts with small tubers (less than 75 g). Sprout growth in larger tubers appears to be unaffected by tuber weight.

There is evidence that selection for small body size in mice results in a decrease in the total number of muscle fibres in a given muscle (Luff & Goldspink, 1967; Hanrahan, Hooper & McCarthy, 1973). It has also been shown that small chickens have fewer muscle fibres in certain muscles than larger chickens (Smith, 1963). This type of work has not, however, been extended to a study of the larger domestic animals. At Göttingen in Germany, Haring et al. (1966) have developed a breed of miniature pig which, at 6 months of age, was about a third of the body weight of commercial pigs. We therefore decided to investigate the muscles of these miniature pigs and compare them with commercial pig muscles, paying particular attention to the number of muscle fibres.